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The lunge, and all of its challenging iterations, are an integral component of a solid lower extremity strengthening program. It also is part of almost every sport in the form of deceleration, lateral agility, kicking, and tackling.

Read any article online or buy any workout program that involves the legs and you will find lunges as a prescribed exercise. The lunge is one of the most commonly performed exercises to build leg strength.

So, wanting to get the most out of your workout, you grab a couple 10 pound dumbbells and go through the first set. Of course, you are very careful to keep your back straight up and down and to complete the exercise you touch your back knee all the way to the ground...

...But what if keeping your back straight increases your risk of injury and what if touching your back knee to the ground increases pressure at the knee?

Biomechanics of Lunges

Recent research has looked at how trunk, knee, and shin position changes pressure at the knees during lunging.

Researchers from Cornell, UMASS Amherst, and the Cybex Research Institute recently studied how trunk and shin position affect joint stresses at the knee. Contrary to popular theory, they found lunging with an upright trunk increased stress at the patellofemoral joint (knee cap). You would think that the lead leg during a lunge takes the most stress; however, their research showed more total joint stress in the knee of the trail limb, especially with an upright trunk (like the picture below).

They reported that there are high joint stresses in the knee in general during the lunge exercise. This can explain why knee pain is common with this exercise.

Lunging with an upright trunk also demands more work from the quadriceps allowing the gluteal muscles to do less work. Research has shown; however, that lunging with a forward trunk and shin posture improves recruitment of the gluteal muscles and decreases joint stress in the trail knee.

After reviewing some research, and looking at the lunge movement, let's dive into the 5 vital variables to track and improve to decrease knee pain.

Lunges: 5 Key Movements Variables

1. Trunk Posture

We have already explored, in the research previously mentioned, how an upright trunk can increase knee joint stress in both knees. To decrease pain at the knee with lunges, employ a forward trunk lean. This can be accomplished by aligning your "chest over your knees" so your buttocks shifts backwards as if to "sit in a chair".

Also be aware of the lateral movement of your trunk during a lunge exercise. Shifting your torso too far towards the lead leg side can decrease gluteal activation and drive up quadriceps usage on the same side. This increased quadriceps demand can increase patellofemoral joint stress.

2. Knee Alignment

Inward Knee Rotation of the Lead Leg It's always a good idea to perform lunges while using a mirror as visual biofeedback. Performing a lunge facing the mirror will give you the best view of the medial and lateral stability of BOTH of your knees. Remember the back leg in the lunge can sometimes take even more stress in the knee than the lead leg.

The key here is not letting your knee track over the instep of your lead leg. If you were to take a laser light and point it straight out from your knee cap, the light should pass over the midpoint of your foot.

Inward Knee Rotation of the Lead Leg

Similarly, if your knee rotates too far outwards, it increases medial joint pressure. This would positioning would affect anyone with degenerative changes or meniscus issues at the medial knee.

3. Pelvis Alignment

Example of Pelvic Drop in The Forward Lunge To perform a proper lunge you need the coordination of your spine, pelvis, hip, knee, and ankle. The pelvis become the forgotten area because it's difficult to observe and can be a challenge to correct properly.

As you load weight onto your lead leg in the lunge, your step side gluteus maximus and medius need to work hard to keep the opposite side hip from dropping. If the opposite hip drops, there is a resultant increased load on the forward leg hip joint and spine. Plus, decreased recruitment of the gluteus muscles yields increased quadriceps usage and additional strain at the knee.

Example of Pelvic Drop in The Forward Lunge

To correct a pelvic drop, imagine "spreading the floor apart" with both feet as this will increase gluteus muscle activation. Also, imagine a string "lifting your trail leg hip to the ceiling" as this will help you visualize the hip hike movement (versus rotation). A elastic band around the knees will help improve your pelvic alignment

4. Step Length

Do you take a long lunge step or short? This question really depends on why you are doing a lunge in the first place. If you are trying to decrease stress at the knee joint than you want to use a slightly longer step length and keep your knee flexion angle no more than 50 degrees (90 degrees would be thigh parallel to the ground).

Use a mirror from a side angle as feedback on step length. Focus on a step distance that allows forward trunk lean and allows your shin bone to be upright.

5. Step vs. Static Lunges

There are many lunge variations and one debated variable is stepping into the lunge versus stepping once and just moving up and down. According to various studies, the "static" lunge (not stepping every time) shows decreased knee joint stress overall. The initial step itself can present with increased joint forces at the knee.

If you are just starting out with lunges it's a good idea to start with a static lunge anyway to help use the proper motion with mirror feedback. Conclusion Adding lunges to your strength training program will help improve lower extremity strength, pelvis control, knee stability, and single leg dynamic control. It is a challenging and fun exercise. By using the 5 keys above, you will be able to decrease the risk of knee pain while performing your lunges.

There are many variations of the lunge that you can add to your program for variety and to target the leg muscles in different ways. You can use the same principles for any of these lunges to help ensure knee protection.